Report on rainwater harvesting system for Shantiniketan Layout, Arekere, Bangalore – revised Submitted by Biome Environmental Solutions Pvt Ltd, (Earlier Rainwater Club) No. 15, 1st Block, 1st Main, BEL Layout, Vidyaranyapura Bangalore – 560 097 www.rainwaterclub.org www.Biome-solutions.com TABLE OF CONTENTS No. Details Page no. 1.0 Client and document details 3 2.0 Overview 3 3.0 Land area and land use 4 4.0 Water supply and consumption 5 5.0 Rainfall and potential runoff 10 6.0 Rainwater harvesting – existing system 17 7.0 Reference images 18 8.0 Resources 20 9.0 Further engagement with Biome 21 10.0 Recommendations for RWH and groundwater recharge 21 List of tables No. Details Page no. TaBle 1 Land use distribution 4 TaBle 2 Borewell details 6 TaBle 3 Open well details 7 TaBle 4 Population calculation for the layout 9 TaBle 5 Water demand calculation 10 TaBle 6 Average rainfall received By Bangalore 10 TaBle 7 Potential runoff for RWH 11 TaBle 8 Annual demand vs. rooftop runoff 11 TaBle 9 Road / paved area runoff details for 20 mm rain 13 TaBle 10 Calculation for 3 x 20 recharge wells for roads/paved areas 13 TaBle 11 Open / unpaved area runoff details for public parks 14 TaBle 12 Calculation for 3 x 20 recharge wells for puBlic parks 14 TaBle 13 Calculation for 6 x 30 recharge wells for puBlic parks 14 TaBle 14 Open / unpaved area runoff details for temple parks 15 TaBle 15 Calculation for 3 x 20 recharge well for Premkala Gelli park 15 TaBle 16 Calculation for 6 x 30 recharge well for Sai Baba Temple 15 TaBle 17 Calculation for 3 x 20 recharge wells for the vacant plots 15 TaBle 18 Calculation for 3 x 20 recharge wells on BWSSB norms 16 List of figures No. Details Page no. Figure 1 Map of Shantiniketan layout 3 Figure 2 Property break-up in the layout 4 Figure 3 Land area and land use 4 Figure 4 Locations of open wells, recharge wells and borewells 5 Figure 5 Images of Borewells, OHT and sumps 6 Figure 6 Images of open wells 8 Figure 7 Images of recharge wells 9 Figure 8 Proposed recharge well locations 16 Figure 9 Current state of some of the drains 17 Figure 10 Nala running through layout 18 2 1.0 Client and document details Client name Shantiniketan Residents Welfare Association Client contact details [email protected], 9980906667 Document date September 27, 2019 Document version Revised 2.0 Overview Biome was invited to visit Shantiniketan Layout, Arekere By the SRWA to understand its water situation and help evolve a way forward for the water resources management at the layout. The overall oBjective of Biome’s engagement is to develop a sustainable rainwater harvesting strategy for the common areas and suggest other water conservation measures that can Be adopted By the community. Shantiniketan Layout is a BDA sanctioned layout that was developed in 1992. The total layout area is aBout 47 acres and is a mix of residential and commercial Buildings, parks and other CA (civic amenities). The residential properties are a combination of independent houses, and small and mid-sized apartments. There are some temples located in the park / CA areas. There are 495 plots with houses, 48 plots with apartments, 115 vacant plots and 21 plots with commercial buildings. Figure 1: Map of Shantiniketan layout The figure Below shows the Break up of the types of properties in the layout – most of them are residential (92.84 %) and very few are commercial. 3 Figure 2: Property break-up in the layout 3.0 Land area and land use The land use distribution shows that 41% area is rooftop, followed By unpaved / open area of 32% and paved / road area of 27%. Land use distribution Area Type of area Sqm Sft Acres % Total layout area 189011 2034514 47 100% Open spaces 61117 657869 15 32% Roads 50836 547199 13 27% Roof area 77058 829447 19 41% Table 1: Land use distribution Figure 3: Land area and land use 4 4.0 Water supply and consumption The main sources of water supply are Cauvery water from BWSSB, which supplies water twice a week to the entire layout, and borewells, the details of which are given Below. About one-third of the houses in the layout have their own borewells. Figure 4: Locations of open wells, recharge wells and borewells 4.1 Borewells Borewell details Borewell Year of Depth Casing Description name digging (ft) (ft) BW1 700 60 Main source of supply to entire layout. It supplies water twice a week - once to half the layout and once to the remaining half. Overall, it serves around 500 plots. On an average, it needs to be pumped for two days to fill up the sump of 5.55 lakh litres and one day to fill up the overhead tank of 1.8 lakh litres. The suBmersiBle pump motor is located aBout 250 meters away, near the UG sump / OHT BW2 450 20 This Borewell is located in the premises of the Sai BaBa temple. The yield has reduced in recent times BW3 The machinery got damaged while digging and re- digging was not attempted. Filled with rocks BW4 300 15 This borewell is located in Shantiniketan Tank Park and is used for watering the park. Yield reduces after 1 hour BW5 Non-yielding borewell located near Shantiniketan Tank Park BW6 550 Located in CA Site Park which takes care of the gardening needs of the park 5 BW7 Located in Vyasa Bank Colony Park, which takes care of the gardening needs of the park. Presently, the motor is under repair BW8 Located near Family Park BW9 Camera inspection has Been done and the report needs to be seen. This borewell is connected to a 14000-litre sump. BW10 Non-yielding borewell Table 2: Borewell details Figure 5: Images of borewells, OHT and sumps 4.2 Open wells The Biome team was aBle to inspect seven open wells. There are a few more wells, yet to be located and inspected. 6 Open well details Open Year of Diameter Depth Static Remarks well digging (ft) (ft) water name level (ft) W1 2' 9" 18 There seems to Be seepage of (pvt) sewage water into the well. The water is used for cleaning, dish washing and clothes washing. Cauvery water is used for cooking, drinking and Bathing. W2 2002 4 24 10 Water is used for the gardening (park) needs of the park in Vasavi Temple W3 4 18 16 First open well in Family Park. (park) Water is used for gardening needs of the park W4 4 26 24 Second open well in Family Park. (park) Has very little water now W5 3 18 This well is used for recharging (pvt) rooftop rainwater. Its water is not used for any purpose, since it is very dirty and sewage water seems to be seeping into the well W6 2003 3 18 8 Water is used for cleaning, car (pvt) washing and flushing toilets W7 3 12 6 Water is used for all uses except (pvt) drinking and cooking Table 3: Open well details 7 Figure 6: Images of open wells 4.3 Recharge wells There are a few recharge wells made By the BBMP in the parks, measuring around 5 ft deep. But none of them are Being maintained. They are filled with deBris or used for composting organic waste. Their inlets are Blocked or completely closed. 8 Figure 7: Images of recharge wells 4.4 Water demand The following assumptions have been made for the purposes of calculation: ● 5 members per residential plot and 2 houses in a plot ● 100 footfalls per preschool ● For smaller commercial properties, footfall of 500 per commercial space The following is a conservative estimate. It was not possiBle to oBtain details of the total supply to the entire layout, as there are multiple sources, which vary across the different properties, and centralized collation of data is not possible. To calculate the water demand for the entire layout, the following assumptions have Been made: ● National Town Planning norms have Been used, which give the figure of 150 LPCD for metro cities and towns with UGD ● For calculating floating population, commercial properties and institutions have been considered ● For calculating demand of floating population, 50 LPCD has Been considered No. of persons in Total Type of property No. of property units each property unit population Preschool (floating) 7 100 700 Restaurant (floating) 2 500 1000 Shop (floating) 9 500 4500 Office (floating) 2 500 1000 Residential house 495 10 4950 Apartment Building 23 60 1380 Total 13530 Table 4: Population calculation for the layout The total population (residents and floating population) is found to Be 13530. The residents number 6330 and the floating population is 7200. 9 The following taBle gives the approximate water demand of Shantiniketan layout: Total water Type of No. of Water usage per person per demand per population people day considered (litres) day (KLD) Residential 6330 150 litres per person 950 Floating population 7200 50 litres per person 360 Total 1310 Table 5: Water demand calculation The daily water demand of Shantiniketan layout is 1310 KL (kilolitres). The monthly demand is 39285 KL and the annual demand is 477968 KL (477.9 million litres). 5.0 Rainfall and potential runoff The average rainfall that Bangalore receives has Been recorded as 970-975 mm with the average number of rainy days as 60. The table Below provides the distriBution of rainfall over the months of the year.